Chromium Nitride – a Chemical Compound

Chromium nitride is a chromium and nitrogen chemical compound with the formula CrN. It is a fantastic coating that offers lubricity as well as superior wear and corrosion resistance. It has a high hardness and corrosion resistance. It is a thin film coating that is extremely hard and inert and is primarily used on precision metal parts.

It is an interstitial compound, with nitrogen atoms filling the octahedral holes in the chromium lattice: it is not strictly a chromium(III) compound, nor does it contain nitride ions (N3). Dichromium nitride, Cr2N, is formed as a second interstitial nitride by chromium. Calico CrN’s high hardness, low coefficient of friction, and low residual stress combine to make it resistant to abrasive, metal-on-metal wear, and galling.

Properties

  • Molecular Weight: 66.0028
  • Appearance: Black powder
  • Melting Point: > 1800 °C
  • Boiling Point: N/A
  • Density: 5.9 g/cm3
  • Solubility in H2O: Insoluble
  • Exact Mass: 65.943582

Synthesis

Chromium(III) nitride can be prepared by direct combination of chromium and nitrogen at 800 °C:

2 Cr + N2 → 2 CrN

It can also synthesize by Physical Vapour Deposition techniques such as Cathodic arc deposition.

Its features are – high toughness, good resistance to corrosion, anti-adhesive and detaching properties, and a reduced coefficient of friction, all this together with a moderate hardness.

Applications

CrN is used as a corrosion-resistant coating material, as well as in metal forming and plastic moulding applications. CrN is frequently found in medical implants and tools. CrN is also a valuable component in advanced multi-component coating systems for hard, wear-resistant applications on cutting tools, such as CrAlN. It has a higher temperature resistance than TiN and is an excellent choice for high-temperature environments. CrN is also effective in corrosive environments and in sliding wear applications.

Magnetism

CrN’s fundamental materials physics, which gives rise to its advantageous properties, has recently been debated in high-profile scientific journals such as Nature Materials. The importance of magnetism in both the low temperature and high-temperature phases has been demonstrated in particular by quantum mechanical calculations of the compound’s electronic structure.

Natural occurrence

Though rare, carlsbergite – the natural form of chromium nitride – occurs in some meteorites.